Systems, methods and apparatus for choked flow element extraction

ABSTRACT

A plasma source includes a ring plasma chamber, a primary winding around an exterior of the ring plasma chamber, multiple ferrites, wherein the ring plasma chamber passes through each of the ferrites and multiple plasma chamber outlets coupling the plasma chamber to a process chamber. Each one of the plasma chamber outlets having a respective plasma restriction. A system and method for generating a plasma are also described.

BACKGROUND

The present invention relates generally to plasma reaction chambers, andmore particularly, to methods, systems and apparatus for plasma reactionchambers separate from the wafer processing chamber.

FIG. 1A is a side view of a typical parallel-plate, capacitive, plasmaprocessing chamber 100. FIG. 1B is a top view of a substrate 102processed in the typical parallel-plate, capacitive, plasma processingchamber 100. The typical plasma processes processing chamber 100includes a top electrode 104, a substrate support 106 for supporting asubstrate to be processed 102. The substrate support 106 can also be abottom electrode. The top electrode 104 is typically a showerhead typeelectrode with multiple inlet ports 109. The multiple inlet ports 109allow process gases 110 in across the width of the processing chamber100.

The typical parallel-plate, capacitive plasma reactor 100 is used forprocessing round planar substrates. Common processes are dielectric etchand other etch processes. Such plasma reactors typically suffer frominherent center-to-edge non-uniformities of neutral species.

Although these systems work well, some produce center-to-edgenon-uniformities of neutral species which arise from the differences inone or more of a flow velocity, an effective gas residence time, and oneor more gas chemistries present at the center of the substrate ascompared to the flow velocity, effective gas residence time, and one ormore gas chemistries present at the edge. The one or more gaschemistries can be caused by gas-phase dissociation, exchange andrecombination reactions.

By way of example, as the process gases are introduced across the widthof the processing chamber the plasma 112 is formed between the topelectrode 104 and bottom electrode 106 and the plasma is formed. Plasmabyproducts 118 are formed by the reaction of radicals and neutrals inthe plasma 112 with the surface of the substrate 102. The plasmabyproducts 118 are drawn off to the sides of the substrate and intopumps 108. Plasma byproducts can include one or more dissociationreactions (e.g., CF4+e⁻→CF3+F+e⁻) and/or one or more ionizations (e.g.,CF4+e⁻→CF3⁺+F) and/or one or more excitations (e.g., Ar→Ar⁺+e⁻) and/orone or more attachments (e.g., CF4+e⁻→CF3+F⁻) and/or one or more binaryreactions (e.g., CF3+H→CF2+HF).

Plasma byproducts 118 can also include etch byproducts including theetchant, F, CFx, SiF2, SiF4, Co, CO2. Etch byproducts can alsodissociate in the plasma 112.

Recombination also occurs during the plasma processing. Recombinationproduces recombination products 120. Recombination typically occurs whenthe radicals and neutrals from the plasma 112 impact surfaces such asthe bottom surface of the top electrode 104. The recombination products120 are then drawn off the side of the substrate 102 into pumps 108,similar to the plasma byproducts 118. Plasma recombination products 120can include one or more wall or surface reactions (e.g., F+CF→CF2,and/or H+H→H2, and/or O+O→O2, and/or N+N→N2). Plasma recombinationproducts 120 can also include deposition where CFx forms a polymer onthe wall or other internal surface of the chamber 100.

It should be noted that as shown in FIG. 1A, the plasma byproducts aredrawn off one side of the substrate 102 and the recombination products120 are drawn off the opposite side of the substrate 102 for claritypurposes only. In actual practice, those skilled in the art wouldrealize that both the recombination products 120 and the plasmabyproducts 118 are intermixed and drawn off both sides of the substrate102 to pumps 108 or other means.

As the plasma processing occurs, concentrations of the recombinationproducts 120 and the plasma byproducts 118 vary from the center to theedge of the substrate 102. As a result, the concentrations of theprocess gases, radicals and neutral species in the plasma 112 alsocorrespondingly vary. Thus, the effective plasma processing, etch inthis instance, varies from the center to the edge of the substrate 102.There are, however, a number of chamber configurations and structuresthat can be implemented to reduce or control the plasma.

With such controls, the plasma radicals and neutral species are mostconcentrated at the center of the substrate 102 in plasma processingregions 114A and 116A over central portion 102A of the substrate 102.Further, the concentrations of the radicals and neutral species aresomewhat less concentrated in intermediate plasma processing regions one114B and 116B over intermediate portion 102B of the substrate 102.Further still, the concentrations of the radicals and neutral speciesare further diluted and less concentrated in edge plasma processingregions 114C and 116C over the edge portion 102C of the substrate 102.

Thus, plasma processing occurs fastest in the center plasma processingregions 114A and 116A over the center portion 102A of substrate 102 ascompared to the plasma processing that occurs slightly slower in theintermediate plasma processing regions 114B and 116B over theintermediate portion 102B of substrate 102 and even slower in the plasmaprocessing of the edge plasma processing regions 114C and 116C over theedge portion 102C of the substrate. This results in a center-to-edgenonuniformity of the substrate 102.

This center-to-edge nonuniformity is exacerbated in small volume productplasma processing chambers that have a very large aspect ratio. Forexample, a very large aspect ratio is defined as when the width W of thesubstrate is about four or more or more times the height H of the plasmaprocessing region. The very large aspect ratio of the plasma processingregion further concentrates the plasma byproducts 118 and recombinationproducts 120 in the plasma processing regions 114A-116C.

Although this center-to-edge non-uniformity of neutral species is notthe only cause of center-to-edge process uniformity, in many dielectricetch applications it is a significant contributor. Specifically,neutral-dependent processes such as gate or bitline mask open,photoresist strip over low-k films, highly selective contact/cell andvia etch may be especially sensitive to these effects. Similar problemsmay apply in other parallel-plate plasma reactors, besides those usedfor wafer dielectric etch.

In view of the foregoing, there is a need for improving thecenter-to-edge uniformity in plasma etch processes.

SUMMARY

Broadly speaking, the present invention fills these needs by providing adistributed multi-zone plasma source. It should be appreciated that thepresent invention can be implemented in numerous ways, including as aprocess, an apparatus, a system, computer readable media, or a device.Several inventive embodiments of the present invention are describedbelow.

One embodiment provides a plasma source includes a ring plasma chamber,a primary winding around an exterior of the ring plasma chamber,multiple ferrites, wherein the ring plasma chamber passes through eachof the ferrites and multiple plasma chamber outlets coupling the plasmachamber to a process chamber. Each one of the plasma chamber outletshaving a respective plasma restriction.

The plasma restriction can have a diameter of between about 0.1 mm andabout 2.0 mm. The plasma restriction can have a diameter less than orequal to twice a plasma sheath thickness. The plasma restriction canhave a diameter sufficient to provide a pressure differential greaterthan about 1.5 to 1 between the plasma chamber and a process chamber.The plasma restriction can be coupled to a bias supply.

The plasma source can include at least one process gas inlet coupling aprocess gas source to the plasma chamber. The plasma source can alsoinclude a process gas flow rate control device coupled to the at leastone process gas inlet.

The ferrites can be substantially evenly distributed around thecircumference of the ring plasma chamber. The ferrites can be grouped ingroups around the circumference of the ring plasma chamber. The ringplasma chamber can be one of a group of shapes consisting ofsubstantially round, substantially triangular, substantiallyrectangular, or substantially polygonal shape.

Another embodiment provides a method of generating a plasma. The methodincludes delivering a process gas into a ring plasma chamber, applying aprimary current to a primary winding around the exterior of the ringplasma chamber, generating magnetic field in the primary winding,concentrating the magnetic field with multiple ferrites. The ring plasmachamber passes through each of the ferrites. A secondary current isinduced in the process gas in the ring plasma chamber and a plasma isgenerated in the process gas in the ring plasma chamber with thesecondary current. The plasma is restricted in the ring plasma chamberwith a plasma restriction in each of multiple plasma chamber outletscoupling the plasma chamber to a process chamber.

The method can also include delivering at least one of a neutral speciesand a radical species to a process chamber through the outlet ports. Theplasma restriction can also be biased.

The method can also include modulating at least one of a flow rate, apressure and/or a bias in the ring plasma chamber. The method can alsoinclude receiving a process feedback signal from at least one processmonitoring sensor and adjusting at least one set point of at least oneof a flow rate, a pressure and/or a bias.

Another embodiment provides a plasma processing system including a ringplasma chamber, a primary winding around an exterior of the ring plasmachamber, multiple ferrites, wherein the ring plasma chamber passesthrough each of the ferrites. Multiple plasma chamber outlets couple theplasma chamber to a process chamber, each one of the plasma chamberoutlets having a respective plasma restriction. The system also includesat least one process monitoring sensor and a controller. The controllerincludes logic for delivering a process gas into the ring plasmachamber, logic for applying a primary current to a primary windingaround the exterior of the ring plasma chamber, logic for generatingmagnetic field in the primary winding, logic for concentrating themagnetic field with the ferrites, logic for inducing a secondary currentin the process gas in the ring plasma chamber, logic for generating aplasma in the process gas in the ring plasma chamber with the secondarycurrent, logic for receiving a process feedback signal from at least oneprocess monitoring sensor and logic for adjusting at least one setpoint.

Yet another embodiment provides a plasma system for processing asubstrate. The system includes a process chamber having a base, multiplesidewalls, a substrate support proximate to the base and a chamber topinterfaced with the sidewalls to enclose the process chamber. The systemalso includes multiple ferrites and multiple plasma chamber outlets. Theferrites are disposed over the chamber top, such that the ferrites aredistributed over regions of the substrate support, the regions extendingat least between an exterior portion of the substrate support and acenter portion of the substrate support. The plasma chamber outlets arecoupling a plasma chamber to the process chamber, each one of the plasmachamber outlets having a respective plasma restriction. The plasmasystem can also include a power supply for providing a current along theferrites, the ferrites concentrating the current over the regions of thesubstrate support.

Other aspects and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings.

FIG. 1A is a side view of a typical parallel-plate, capacitive, plasmaprocessing chamber.

FIG. 1B is a top view of a substrate processed in the typicalparallel-plate, capacitive, plasma processing chamber.

FIG. 2A is a perspective view of a plasma source, in accordance with anembodiment of the present invention.

FIG. 2B is a top view of a plasma source, in accordance with anembodiment of the present invention.

FIG. 2C is a sectional view 2C-2C of a plasma source, in accordance withan embodiment of the present invention.

FIG. 2D is a perspective sectional view of a plasma source, inaccordance with an embodiment of the present invention.

FIG. 2E is a perspective view of a plasma source mounted on a processchamber, in accordance with an embodiment of the present invention.

FIGS. 2F and 2G are additional perspective views of a plasma source 200mounted on a process chamber, in accordance with an embodiment of thepresent invention.

FIG. 2H is another perspective view of a plasma source mounted on aprocess chamber 230, in accordance with an embodiment of the presentinvention.

FIG. 2I shows multiple sectional views of the plasma chamber outlets, inaccordance with embodiments of the present invention.

FIG. 2J is a process chamber view of multiple plasma chamber outlets, inaccordance with embodiments of the present invention.

FIG. 3A is a perspective view of another plasma source, in accordancewith an embodiment of the present invention.

FIG. 3B is a top perspective view of a multizone plasma source, inaccordance with an embodiment of the present invention.

FIG. 3C is a bottom perspective view of multizone plasma source, inaccordance with an embodiment of the present invention.

FIG. 3D is a top perspective view of another multizone plasma source, inaccordance with an embodiment of the present invention.

FIG. 3E is a bottom perspective view of multizone plasma source, inaccordance with an embodiment of the present invention.

FIGS. 4A and 4B are simplified schematic views of multizone plasmasources, in accordance with an embodiment of the present invention.

FIG. 5 is a flow and pressure graph for various sizes of the optionalplasma restriction, in accordance with an embodiment of the presentinvention.

FIG. 6A is a schematic of an exemplary transformer, in accordance withan embodiment of the present invention.

FIG. 6B is a schematic of a single ring of ferrites and plasma chamberin a plasma source, in accordance with an embodiment of the presentinvention.

FIG. 7 is an electrical schematic of a single ring of ferrites andplasma chamber in a multizone plasma source, in accordance with anembodiment of the present invention

FIG. 8 is an electrical schematic of a power supply, in accordance withan embodiment of the present invention.

FIGS. 9A-9C are flow diagrams of the flow from the plasma source, inaccordance with an embodiment of the present invention.

FIG. 10 is a flowchart diagram that illustrates the method operationsperformed in operation of the plasma sources described herein, inaccordance with one embodiment of the present invention.

FIG. 11 is a block diagram of an integrated system including one or moreof the plasma sources described herein, in accordance with an embodimentof the present invention.

DETAILED DESCRIPTION

Several exemplary embodiments for a distributed multi-zone plasma sourcesystem, method and apparatus will now be described. It will be apparentto those skilled in the art that the present invention may be practicedwithout some or all of the specific details set forth herein.

FIG. 2A is a perspective view of a plasma source 200, in accordance withan embodiment of the present invention. The plasma source 200 includes aprocess gas inlet 206, multiple ferrites 204, a plasma source top 208and a chamber top 202. It should be understood that the specificarrangement of the elements 202-208 of the plasma source 200 might bemodified from what is shown. For example, the chamber top 202 and theplasma source top 208 could be combined into a single cover of theprocess chamber 230.

FIG. 2B is a top view of a plasma source 200, in accordance with anembodiment of the present invention. FIG. 2C is a sectional view 2C-2Cof a plasma source 200, in accordance with an embodiment of the presentinvention. FIG. 2D is a perspective sectional view of a plasma source200, in accordance with an embodiment of the present invention. FIG. 2Eis a perspective view of a plasma source 200 mounted on a processchamber 230, in accordance with an embodiment of the present invention.A process gas plenum 212 is shown as a distributing plenum for theprocess gas supplied from the process gas inlet 206.

Process gas 110 flows into the inlet port 206 to the process gas plenum212. The process gas plenum 212 distributes the process gas 110 to inletports 212A. The inlet ports 212A direct the process gas 110 into theplasma chamber 210. The process gas inlet ports 212A can be aligned withor offset from the plasma chamber outlets 220. The process gas inletports 212A and/or the plasma chamber outlets 220 can be located betweenthe ferrites 204 or aligned with the ferrites or combinations thereof.

The ferrites 204 wrap around the plasma chamber 210 at selectedintervals. The ferrites 204 concentrate the magnetic field sufficient tocause the electric field proximate to the center of each ferrite to bestrong enough to support a plasma at a corresponding point in the plasmachamber 210.

The ferrites 204 are shown as being substantially square however, aswill be shown below, the ferrites can be other shapes. The ferrites 204are shown as being made in multiple parts 224A, 224B, 224C, 224D,however the ferrites can be in one or more parts. The multiple ferriteparts 224A, 224B, 224C, 224D are substantially close together asrequired to concentrate the electric field proximate to the center ofeach ferrite 204. The ferrites 204 are shown distributed about thechamber top 202. The process chamber 230 has sidewalls 230′ and base230″. The substrate support 106 is on or near or proximate to the base230″.

Plasma chamber outlets 220 are shown coupling the plasma chamber 210 tothe process chamber 230 below the chamber top 202. The plasma chamberoutlets 220 deliver plasma and/or radical and/or neutral species fromthe plasma chamber 210 and into the process chamber 230.

An optional plasma restriction 214 is also shown. The optional plasmarestriction 214 can be used to provide a desired pressure differentialbetween the plasma chamber 210 and the process chamber 230. The optionalplasma restriction 214 can also be small enough and/or be biased suchthat plasma is substantially prevented from passing from the plasmachamber 210 to the process chamber 230. In addition, the plasmarestriction can be biased to extract ions from the plasma chamber 210and draw the ions into the process chamber and then onto the wafer. Byway of example the optional plasma restriction 214 can have a diameterthat is less than or equal to twice a plasma sheath thickness and thusthe plasma sheath can prevent the plasma from passing through theoptional plasma restriction. The optional plasma restriction 214 canhave a selected diameter between about 0.1 mm and about 2.0 mm (e.g.,0.1 mm, 0.2 mm, 0.5 mm, 1.0 mm, 2.0 mm). It should be noted that theaspect ratio of the optional plasma restriction 214 can be used toadjust the effectiveness of plasma restriction. By way of example, ahigher aspect ratio (i.e., length/width) plasma restriction 214 cansubstantially restrict the plasma while having minimal impact on neutralor radical species transport. It should also be understood that largerdiameter outlet orifices are can also be used. By way of example theoptional plasma restriction 214 can be omitted and the effectiverestriction is the width of the plasma chamber outlets 220. The width ofthe plasma chamber outlets 220 can be substantially wide enough to allowa substantially equal pressure in both the plasma chamber 210 and theprocess chamber 230.

FIG. 2I shows multiple sectional views of the plasma chamber outlets220, in accordance with embodiments of the present invention. FIG. 2J isa process chamber view of multiple plasma chamber outlets 220, inaccordance with embodiments of the present invention. The plasma chamberoutlets 220 can be a straight through, substantially cylindrical with asubstantially rectangular, cross-sectional shape of the desired width.The plasma chamber outlets 220 can include an optional conical shape220A. The optional conical shape 220A can provide flow smoothing and/orflow distribution from the plasma chamber outlets 220. The plasmachamber outlets 220 can also include other optional shapes. By way ofexample the plasma chamber outlets 220 can include a larger width of thesame shape 220B or a smaller width of the same shape 220F. The plasmachamber outlets 220 can include an optional curved or bowl shaped outlet220C, 220E. The optional curved or bowl shaped outlet 220C, 220E canhave an opening at the widest point such as outlet 220C or at a narrowerpoint less than the widest point such as outlet 220E. The optionalconical shape can be a truncated conical shape 220D.

The optional plasma restriction can be located substantially centralalong the length of the outlet port 220 such as the optional plasmarestriction 214. Alternatively, the optional plasma restriction can belocated substantially at the plasma chamber 210 end of the outlet port220 such as the optional plasma restriction 214′. Alternatively, theoptional plasma restriction can be located substantially at the processchamber 230 end of the outlet port 220 such as the optional plasmarestriction 214″. It should be understood that the optional plasmarestriction 214 can be located anywhere along the length of the outletport 220 between the plasma chamber 210 end and the process chamber 230end of the outlet port 220.

As shown in FIG. 2J, the plasma chamber outlet 220 can be any suitableshape. By way of example, substantially round 220, substantiallyelliptical 220H, substantially rectangular 2201, 220J, or othergeometrical shapes (e.g., triangular 220K, polygon of any number ofsides 220L). The plasma chamber outlet 220 can include substantiallysharp edges 2201, 220K, 220L or substantially curved edges and/or sides220J, 220M, 220N. Combination of shapes can also be included in theplasma chamber outlet 220. By way of example optional conical shape 220Acan have a more elliptical shape 220A′ rather than a substantially roundshape 220A.

The chamber top 202 can also include one or more outlets 234. Theoutlets 234 are coupled to a lower pressure source (e.g., a vacuumpump). The outlets 234 allow the lower pressure source to withdraw theplasma byproducts 118 and recombination products 120 from near thecenter of the process chamber 230. As a result, the plasma byproducts118 and recombination products 120 do not interfere with the plasma 410and the neutral species 412 generated by the plasma in the processchamber.

The process chamber 230 includes load ports 232 and support structurefor supporting the substrate to be processed. Other features may also beincluded in the process chamber 230 as are well known in the art.

FIGS. 2F and 2G are additional perspective views of a plasma source 200mounted on a process chamber 230, in accordance with an embodiment ofthe present invention. The plasma source top 208 is shown lifted (FIG.2F) and removed (FIG. 2G) for description of additional details. Theplasma chamber 210 can be constructed of a different material than theplasma source top 208 or the process chamber 230. By way of example, theplasma chamber 210 can be a ceramic and the plasma source top 208 or theprocess chamber 230 could be ceramic, metal (e.g., aluminum, steel,stainless steel, etc.). Slots 226A and 226B are provided for the supportand installation of the ferrites 204.

As shown in FIG. 2G the ferrites 204 are shown wrapping around theexterior of plasma chamber 210. The plasma chamber 210 can be formed ofa dielectric such as a ceramic or other dielectric material (e.g.,quartz, silica (siO2), alumina (Al2O3), sapphire (Al2O3), aluminumnitride (AlN), yttrium oxide (Y2O3) and/or similar materials andcombinations thereof).

FIG. 2H is another perspective view of a plasma source 200 mounted on aprocess chamber 230, in accordance with an embodiment of the presentinvention. As shown in FIG. 2H, a primary conductor 240 is shown wrappedaround the plasma chamber 210. The primary conductor 240 is the primarywinding of an inductive element as will be described in more detail inFIG. 7 below. The primary conductor 240 has one or more turns around theplasma chamber 210. As shown here, the primary conductor 240 has twoturns around the plasma chamber 210, however more than two turns couldalso be used.

FIG. 3A is a perspective view of another plasma source 300, inaccordance with an embodiment of the present invention. The plasmasource 300 includes plasma chamber 210 having multiple ferrite elements204 surrounding the plasma chamber at selected intervals. In thisinstance the ferrite elements 204 surrounding the plasma chamber atsubstantially equal intervals but they could be at different intervals.

The plasma chamber 210 can be roughly circular or geometrically shaped,such as in this instance, having five sides. Similarly, the plasmachamber 210 could be circular or three or more sided geometrical shapes.It should also be noted that the plasma chamber 210 could have anapproximately rectangular or approximately circular or roundedcross-sectional shape. The inner surfaces of the plasma chamber 210 canbe smoothed and without any sharp (e.g., about perpendicular or moreacute angle) edges or corners. By way of example, the inner corners canhave a rounded contour with a relatively large radius (e.g. betweenabout ½ and about twice the radius of a cross-section of the plasmachamber). It should also be noted that while a single process gas inlet206 is shown coupled to the plasma chamber 210, two or more process gasinlet's could be used to supply process gas to the plasma chamber.

FIG. 3B is a top perspective view of a multizone plasma source 320, inaccordance with an embodiment of the present invention. The multizoneplasma source 320 includes multiple, individual, concentric plasmachambers 310A-310D, e.g., in nested rings. Each of the concentric plasmachambers 310A-310D has a corresponding set of ferrites 204A-204D.

FIG. 3C is a bottom perspective view of multizone plasma source 320, inaccordance with an embodiment of the present invention. The chamber top202 has multiple process outlet ports 304A-304E and multiple plasmaoutlet ports 220A-220D. The multiple plasma outlet ports 220A-220D arecoupled to corresponding plasma chambers 310A-310D.

FIG. 3D is a top perspective view of another multizone plasma source330, in accordance with an embodiment of the present invention. FIG. 3Eis a bottom perspective view of multizone plasma source 330, inaccordance with an embodiment of the present invention. The multizoneplasma source 330 includes multiple concentric plasma chambers310A-310E. Each of the concentric plasma chambers 310A-310E has acorresponding set of ferrites 204A-204E.

As shown the ferrites 204A-204E of adjacent plasma chambers 310A-310Ecan overlap slightly as shown in regions 332A-332D. By way of example,inner edges of ferrites 204B overlap the outer edges of ferrites 204A inregion 332A. Similarly, outer edges of ferrites 204B overlap the inneredges of ferrites 204C in region 332B. The overlapping ferrites204A-204E allow the concentric plasma chambers 310A-310E to be moreclosely packed in the multizone plasma source 330. Thus allowing moreconcentric rings 310A-310E (e.g., five concentric rings) to be includedin the same diameter as non-overlapping ferrite embodiment shown inFIGS. 3B and 3C having only four concentric rings 310A-310D. As will bedescribed below, each ring 310A-310E can be individually controlled inbias, gas flow, concentration, RF power, etc. Thus, a greater number ofconcentric rings 310A-310E provides a more fine tuning control of theprocess across the diameter of the substrate 102 in the process chamber230.

The ferrites 204A-204E can optionally be arranged in multiple radialsegments (i.e., pie slice shapes) 334A-334L of the multizone plasmasource 330. As will be described below, each radial segment 334A-334Lcan be individually controlled in bias, gas flow, concentration, etc.Thus, the radial segments 334A-334L provide yet another fine tuningcontrol of the process radially across the substrate 102 in the processchamber 230.

FIGS. 4A and 4B are simplified schematic views of multizone plasmasources 300, 320, in accordance with an embodiment of the presentinvention. The chamber top 202 includes the multizone plasma sources300, 320. The process chamber 230 has sidewalls 230′ and base 230″. Thesubstrate support 106 is on or near or proximate to the base 230″. Theprocess outlet ports 304A-304E withdraw the plasma byproducts 118 andrecombination products 120 substantially equally across the width W ofthe substrate 102. As a result, the plasma byproducts 118 andrecombination products 120 do not interfere with the plasma 410 and theneutral species 412 generated by the plasma. The neutral species 412 aretherefore substantially evenly distributed across the width of thesubstrate 102. The neutral species 412 react with the surface of thesubstrate 102. As the neutral species 412 are substantially evenlydistributed across the width of the substrate 102, the center-to-edgenon-uniformities of the plasma processes (e.g., etch, strip or otherplasma processes) applied in the processing chamber 230 are alsosubstantially eliminated.

A controller 420 includes corresponding controls 422A-422E (e.g.,software, logic, set points, recipes, etc.) for each ring 310A-310E.Process monitoring sensors 424, 426 can also be coupled to thecontroller 420 to provide a process feedback. The controls 422A-422E canindividually control each ring 310A-310E such as a bias signal, power,frequency, process gas 110 pressures, flow rates and concentrations.Thus providing a radial profile control of dissociated gas across thediameter of the substrate 102 in the process chamber 230.

Each of the multiple plasma chambers 310A-310E can be controlledindependently to manipulate the processes in the corresponding region ofthe processing chamber 230.

Similarly, each of the multiple radial segments 334A-334L allows eachradial segment of the multiple plasma chambers 310A-310E to becontrolled independently to manipulate the processes in thecorresponding region of the processing chamber 230. By way of example, aprocess variable set point for the flow rate and pressure of the processgas 110 in the plasma chamber 310B is input to the corresponding control422B. At least one of the process monitoring sensors 424, 426 provides aprocess measurement input to the corresponding control 422B. Based onthe process measurement input from the process monitoring sensors 424,426 and the logic and software, the corresponding control 422B thenoutputs revised setpoints for the RF power to ferrites 310B and the flowrate and the pressure of the process gas 110 in the plasma chamber 310B.

Similarly, the processes can be monitored and/or controlled in each ofthe respective regions defined by one or more or a combination of theconcentric ring plasma chambers 310A-E, and/or the ferrites 204A-E,and/or the radial segments 334A-334L of the multizone plasma sources200, 300, 310, 320, 330. It should also be understood that each of thezones could be operated in the same manner and setpoints so that themultizone plasma sources 200, 300, 310, 320, 330 are effectively asingle zone plasma source. Further, some of the zones of the multizoneplasma sources 200, 300, 310, 320, 330 can be operated in the samemanner and setpoints so that the multizone plasma sources have lesszones.

FIG. 5 is a flow and pressure graph for various sizes of the optionalplasma restriction 214, in accordance with an embodiment of the presentinvention. Graph 510 is the flow rate in standard cubic centimeters perminute (SCCM) for an optional plasma restriction 214 having a diameterof 0.2 mm. Graph 520 is the flow rate for an optional plasma restriction214 having a diameter of 0.5 mm. Graph 530 is the flow rate for anoptional plasma restriction 214 having a diameter of 1.0 mm. As can beseen, the various sizes of the optional plasma restriction 214 candetermine a pressure drop between the plasma chamber 210 and the processchamber 230. If the pressure drop is such that choked flow occurs acrossthe plasma restriction 214, the mass flow rate into the process chamber210 will not increase with a decrease in the plasma chamber whenpressure in the plasma chamber 210 is constant.

Increasing the pressure in the plasma chamber 210 provides the densityof the process gas 110 sufficient to support a plasma in the plasmachamber. For a fixed RF voltage, the current required to be induced intothe process gas 110 is inversely proportional to the process gaspressure. Therefore, increasing the process gas 110 pressure in theplasma chamber 210 reduces the current required to produce the plasma.Further, since the plasma requires the process gas pressure to supportthe plasma, then the plasma will be contained in the plasma chamber 210and will not flow from the plasma chamber into the process chamber 230.As a result, the plasma restriction 214 can restrict the plasma to theplasma chamber 210.

A transformer has a primary winding and a secondary winding. A primarycurrent through the primary winding generates a magnetic field. As themagnetic field passes through the secondary winding, a correspondingsecondary current is induced into the secondary winding. A transformerwith a ferrite core, concentrates (i.e., focuses) the magnetic field toa smaller, denser magnetic field and therefore more efficiently inducesthe secondary current into the secondary winding. This allows for veryefficient low frequency operation (e.g., less than about 13 MHz and morespecifically between 10 kHz and less than about 5 MHz and morespecifically between about 10 kHz and less than about 1 MHz). The lowfrequency operation also provides significantly lower cost relative totypical high frequency RF plasma systems (e.g., about 13.56 MHz andhigher frequencies).

A further advantage of low frequency ferrite coupled plasma systems istheir low ion bombardment energies, which results in less plasma erosionand fewer on-wafer particulates relative to a high-frequency RF system.Less plasma erosion results in less wear and tear on the plasma chamber210 surfaces and components.

FIG. 6A is a schematic of an exemplary transformer 600, in accordancewith an embodiment of the present invention. A primary current I_(p) isapplied to the primary winding 620 from a power supply. The flow of theprimary current I_(p) through the primary winding 620 produces amagnetic field 622 into the ferrite 204. The magnetic field 622 emergesfrom the ferrite in the center of the secondary winding 630 and inducesa secondary current I_(s) in the secondary winding.

FIG. 6B is a schematic of a single ring of ferrites 204 and plasmachamber 210 in a plasma source 200, 300, 310, 320, 330, in accordancewith an embodiment of the present invention. FIG. 7 is an electricalschematic 700 of a single ring of ferrites 204 and plasma chamber 210 ina plasma source 200, 300, 310, 320, 330, in accordance with anembodiment of the present invention. In the plasma sources 200, 300,310, 320, 330, described herein, the primary winding 240 is wrappedaround each plasma chamber 210 and inside each respective set offerrites 204, 204A-E. The secondary winding is the process gas 110inside the plasma chamber 210.

A primary current I_(p) is applied to the primary winding 240 from apower supply 702. The power can be RF (e.g., about 10 kHz to about 1 MHzor more or between about 10 kHz to about 5 MHz or between about 10 kHzto less than about 13 MHz). The flow of the primary current I_(p)through the primary winding 240 produces a magnetic field 622 in theferrites 204. The magnetic field 622 induces a secondary current I_(s)in the process gas 110 inside the plasma chamber 210. As a result, theprocess gas is excited sufficiently to form a plasma 410.

FIG. 8 is an electrical schematic of a power supply 702, in accordancewith an embodiment of the present invention. The power supply 702includes a rectifier 804 for converting the AC power from the powersource 802 into a DC power. The filter 808 filters the output of therectifier 804. The filtered DC is delivered to the inverter 810 from thefilter 808. The inverter 810 converts the filtered DC to an AC signal atthe desired frequency, voltage and current. A resonant circuit 812matches resonance with the plasma chamber load 814 so as to efficientlydeliver the desired AC signal to the load in resonance.

A controller 820 controls the power supply 702. The controller 820includes a user interface 822 that may include a link (e.g., network) toa system controller or a larger area control system (not shown). Thecontroller 820 is coupled to the Components 804, 808, 810, 812 directlyand via sensors 806A, 806B, 806C for monitoring and controlling theoperation thereof. By way of example the controller 820 monitors one ormore of the voltage, current, power, frequency and phase of the powersignals within the power supply 702.

FIGS. 9A-9C are flow diagrams of the flow from the plasma source 300,310, 320, 330, in accordance with an embodiment of the presentinvention. The radicals and neutrals flow 902 are shown flowing from theplasma chamber 304A-F toward a substrate 102 in an approximate fanshape. The fan shape begins at the outlet ports 220 and expands as itapproaches the wafer 102. The gas flowing through the plasma chamber304A-F has a flowrate Q and a pressure Ps. The pressure Pc is thepressure in the process chamber 230. The difference between Ps and Pcallows the radicals and neutrals flow 902 to expand toward the wafer102.

Referring now to FIG. 9B, the concentration 920 of the radicals andneutrals flow 902 is a function of the distance L between the outletports 220 and the height H of the process chamber 230. If the distance Lbetween the outlet ports 220 is too great then there will be regions 904where the concentration 920 of the radicals and neutrals flow 902 isinsufficient to react with the surface of the wafer 102. Similarly, ifthe height H of the process chamber 230 is too small, then there will beregions 904 where the concentration 920 of the radicals and neutralsflow 902 is insufficient to react with the surface of the wafer 102.FIG. 9C shows an ideal relationship of Height H and distance L asfollows:

R = R(x, H, L) Where:  R(x) = (n_(total) − n₀)/n₀  and${n_{total}(x)} = {\sum\limits_{i}n_{i}}$

If distance L is approximately equal to height H/2 the variation ofconcentration of the radicals and neutrals across the surface of thewafer can be minimized. Alternatively, increasing or decreasing therelationship of distance L and height H can allow variation inconcentration of the radicals and neutrals across the surface of thewafer.

FIG. 10 is a flowchart diagram that illustrates the method operationsperformed in operation of the plasma source 200, 300, 310, 320, 330, inaccordance with one embodiment of the present invention. The operationsillustrated herein are by way of example, as it should be understoodthat some operations may have sub-operations and in other instances,certain operations described herein may not be included in theillustrated operations. With this in mind, the method and operations1000 will now be described.

In an operation 1005, a process gas 110 is delivered to a plasma chamber210. In an operation 1010, the process gas 110 is maintained at a firstpressure in the plasma chamber 210. The first pressure can be the sameas or up to twice or more multiples of a pressure of a process chamber230 coupled to a set of outlet ports 220 of the plasma chamber.

In an operation 1015, a primary current I_(p) is applied to a primarywinding 240 wrapped around the external circumference of the plasmachamber 210. In an operation 1020, the primary current I_(p) generates amagnetic field. In an operation 1025, one or more ferrites 204concentrate the magnetic field to the approximate center portion of theplasma chamber 210. The ferrites 204 are formed around the plasmachamber 230.

In an operation 1030, the magnetic field induces a secondary currentI_(s) in the process gas 110 in the plasma chamber 210. In an operation1035, the secondary current I_(s) generates a plasma in the process gas110 in the plasma chamber 210. In an operation 1040, a portion of theplasma and plasma generated radicals and neutrals pass from the plasmachamber 210 through the plasma chamber outlets 220 and into the processchamber 230.

In an operation 1045, the radicals and neutrals interact with asubstrate 102 and the processing chamber 230 to produce plasmabyproducts 118 and recombination products 120. In an operation 1050, theplasma byproducts 118 and the recombination products 120 are drawn outof the processing chamber through one or more process outlet ports304A-304E. The one or more process outlet ports 304A-304E aredistributed across the surface of the process chamber top 202 or alongthe edges of the substrate support 106 or below the substrate supportsuch as in the base of the process chamber or combinations thereof andthe method operations can end.

FIG. 11 is a block diagram of an integrated system 1100 including theplasma sources 200, 300, 320, in accordance with an embodiment of thepresent invention. The integrated system 1100 includes the plasmasources 200, 300, 320, and an integrated system controller 1110 coupledto the plasma sources. The integrated system controller 1110 includes oris coupled to (e.g., via a wired or wireless network 1112) a userinterface 1114. The user interface 1114 provides user readable outputsand indications and can receive user inputs and provides user access tothe integrated system controller 1110.

The integrated system controller 1110 can include a special purposecomputer or a general purpose computer. The integrated system controller1110 can execute computer programs 1116 to monitor, control and collectand store data 1118 (e.g., performance history, analysis of performanceor defects, operator logs, and history, etc.) for the plasma sources200, 300, 320. By way of example, the integrated system controller 1110can adjust the operations of the plasma sources 200, 300, 320 and/or thecomponents therein (e.g., the one of the concentric ring plasma chambers310A-E or ferrites 204, 204A-E, etc.) if data collected dictates anadjustment to the operation thereof.

With the above embodiments in mind, it should be understood that theinvention may employ various computer-implemented operations involvingdata stored in computer systems. These operations are those requiringphysical manipulation of physical quantities. Usually, though notnecessarily, these quantities take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared, andotherwise manipulated. Further, the manipulations performed are oftenreferred to in terms, such as producing, identifying, determining, orcomparing.

Any of the operations described herein that form part of the inventionare useful machine operations. The invention also relates to a device oran apparatus for performing these operations. The apparatus may bespecially constructed for the required purposes, or it may be ageneral-purpose computer selectively activated or configured by acomputer program stored in the computer. In particular, variousgeneral-purpose machines may be used with computer programs written inaccordance with the teachings herein, or it may be more convenient toconstruct a more specialized apparatus to perform the requiredoperations.

The invention can also be embodied as computer readable code and/orlogic on a computer readable medium. The computer readable medium is anydata storage device that can store data which can thereafter be read bya computer system. Examples of the computer readable medium include harddrives, network attached storage (NAS), logic circuits, read-onlymemory, random-access memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes,and other optical and non-optical data storage devices. The computerreadable medium can also be distributed over a network coupled computersystems so that the computer readable code is stored and executed in adistributed fashion.

It will be further appreciated that the instructions represented by theoperations in the above figures are not required to be performed in theorder illustrated, and that all the processing represented by theoperations may not be necessary to practice the invention. Further, theprocesses described in any of the above figures can also be implementedin software stored in any one of or combinations of the RAM, the ROM, orthe hard disk drive.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims.

1. A plasma source comprising: a ring plasma chamber; a primary windingaround an exterior of the ring plasma chamber; a plurality of ferrites,wherein the ring plasma chamber passes through each of the plurality offerrites; and a plurality of plasma chamber outlets coupling the plasmachamber to a process chamber, each one of the plurality plasma chamberoutlets having a respective plasma restriction.
 2. The plasma source ofclaim 1, wherein the plasma restriction has a diameter of between about0.1 mm and about 2.0 mm.
 3. The plasma source of claim 1, wherein theplasma restriction has a diameter less than or equal to twice a plasmasheath thickness.
 4. The plasma source of claim 1, wherein the plasmarestriction has a diameter sufficient to provide a pressure differentialgreater than about 1.5 to 1 between the plasma chamber and a processchamber.
 5. The plasma source of claim 1, wherein the plasma restrictionis coupled to a bias supply.
 6. The plasma source of claim 1, furthercomprising at least one process gas inlet coupling a process gas sourceto the plasma chamber.
 7. The plasma source of claim 6, furthercomprising a process gas flow rate control device coupled to the atleast one process gas inlet.
 8. The plasma source of claim 1, whereinthe ferrites are substantially evenly distributed around thecircumference of the ring plasma chamber.
 9. The plasma source of claim1, wherein the ferrites are in a plurality of groups around thecircumference of the ring plasma chamber.
 10. The plasma source of claim1, wherein the ring plasma chamber is one of a group of shapesconsisting of substantially round, substantially triangular,substantially rectangular, or substantially polygonal shape.
 11. Amethod of generating a plasma comprising: delivering a process gas intoa ring plasma chamber; applying a primary current to a primary windingaround the exterior of the ring plasma chamber; generating magneticfield in the primary winding; concentrating the magnetic field with aplurality of ferrites, wherein the ring plasma chamber passes througheach of the plurality of ferrites; inducing a secondary current in theprocess gas in the ring plasma chamber; generating a plasma in theprocess gas in the ring plasma chamber with the secondary current; andrestricting the plasma in the ring plasma chamber with a plasmarestriction in each of a plurality of plasma chamber outlets couplingthe plasma chamber to a process chamber.
 12. The method of claim 11,further comprising delivering at least one of a neutral species and aradical species to a process chamber through the plurality of outletports.
 13. The method of claim 11, wherein the plasma restriction has adiameter of between about 0.1 mm and about 2.0 mm.
 14. The method ofclaim 11, wherein the plasma restriction has a diameter less than orequal to twice a plasma sheath thickness.
 15. The method of claim 11,wherein the plasma restriction has a diameter sufficient to provide apressure differential greater than about 1.5 to 1 between the plasmachamber and a process chamber.
 16. The method of claim 11, furthercomprising biasing the plasma restriction.
 17. The method of claim 11,further comprising modulating at least one of a flow rate, a pressureand/or a bias in the ring plasma chamber.
 18. The method of claim 11,further comprising receiving a process feedback signal from at least oneprocess monitoring sensor and adjusting at least one set point of atleast one of a flow rate, a pressure and/or a bias.
 19. A plasmaprocessing system comprising: a ring plasma chamber; a primary windingaround an exterior of the ring plasma chamber; a plurality of ferrites,wherein the ring plasma chamber passes through each of the plurality offerrites; a plurality of plasma chamber outlets coupling the plasmachamber to a process chamber, each one of the plurality plasma chamberoutlets having a respective plasma restriction; at least one processmonitoring sensor; and a controller including: logic for delivering aprocess gas into a ring plasma chamber; logic for applying a primarycurrent to a primary winding around the exterior of the ring plasmachamber; logic for generating magnetic field in the primary winding;logic for concentrating the magnetic field with the plurality offerrites; logic for inducing a secondary current in the process gas inthe ring plasma chamber; logic for generating a plasma in the processgas in the ring plasma chamber with the secondary current; logic forreceiving a process feedback signal from at least one process monitoringsensor; and logic for adjusting at least one set point.
 20. A plasmasystem for processing a substrate, comprising: a process chamber having:a base; a plurality of sidewalls; a substrate support proximate to thebase; and a chamber top interfaced with the sidewalls to enclose theprocess chamber; a plurality of ferrites disposed over the chamber top,such that the plurality of ferrites are distributed over regions of thesubstrate support, the regions extending at least between an exteriorportion of the substrate support and a center portion of the substratesupport; and a plurality of plasma chamber outlets coupling a plasmachamber to the process chamber, each one of the plurality plasma chamberoutlets having a respective plasma restriction.
 21. The plasma system ofclaim 20, further comprising: a power supply for providing a currentalong the plurality of ferrites, the plurality of ferrites concentratingthe current over the regions of the substrate support.